What a lot of work. You've worked out what your business is, set your goals, made sure your customers actually exist, created a cashflow forecast, looked at all the legal stuff and prepared, worked out where you are getting the money to start and put together a marketing plan. What next?
Next is to make sure that all of the bits feed each other. Your cashflow forecast should have a budget to pay for your marketing plan. Your marketing plans should reflect the goals and values of your business. You should know what you need to do to make sure you meet all legal requirements.
Once you have your plans polished and they feel pretty good you should take a step back and decide whether to press 'go'.
Pressing that button is hard, especially since every business plan is made up of a certain level of educated guesses and assumptions. The only way to really know what mistakes you have made in your planning is to test your plan, and the only way to do that is to enact it.
So if you honestly believe that your business has a reasonable chance of success - go for it. Your plan will never be perfect and and some point you will need to take the leap. But your business plan gives a blueprint that will maximise your chances of success and help you to avoid some of the pitfalls.
Once you have started, don't feel that you have to stick to your plan. A plan is just a guideline. Opportunities will come up and failures will occur that you never expected. Play to your strengths and find other people who can do the tasks that you are weak at. Be flexible, be prepared to change and be prepared to be uncomfortable, but always keep your eye on your personal and business goals and always assess a new opportunity before following it.